If all someone is doing on this site or any other is to steer traffic to their own website, they're here for the wrong reason. If they go to church just to make connections and enlarge their "network", they are there for the wrong reason. If I came to your church to recruit members for my church, you would rightly resent that.
Having said that, we do not ban people for posting a link to their site in their signature and we do have a subforum under Computers and Internet called the Site Showcase where one can talk about their site. We have banned people when it became clear that their purpose here was to steer traffic to their site rather than to fellowship here.
The OP is a legitimate question, particularly when talking about essentially secular sites. But if God has given someone a message, won't He also help to get that message out? Perhaps the first step in such a case is to look to God and see if what one wants to bring to people is what He wants brought to them.